Supermarket trolleys are familiar devices, and almost no customer can manage without a trolley. As a result, the supermarket trolley may serve as a point of reference for and of the customer during his/her visit to the supermarket.
The conventional technique for purchasing items generally consists of the following. A customer enters the store and travels along the aisles with his shopping trolley, and selects and inserts into the trolley the items he wishes to purchase. When the customer completes his shopping, he comes to the cashier, who takes out each item and scans a bar code presented thereon, thereby entering the data indicative of the item's price (and possible discounts) into a computer that calculates the entire sum to be paid by the customer.
Items in the supermarket may be provided with security tags, for example, magnetic tags aimed at avoiding thefts. Such a magnetic tag typically comprises two magnetic strips made of, respectively, hard magnetic and soft magnetic materials. The hard magnetic strip is shiftable between its passive state, in which it allows the detection of a response of the soft magnetic strip to an external magnetic field generated by the security system in the exit gate, and its active state, in which it prevents the detection of the response of the soft magnetic strip. In other words, the passive state of the hard magnetic strip corresponds to the active state of a magnetic tag, in which it can be detected, and the active state of the hard magnetic strip corresponds to the passive state of the tag, in which it is non-detectable. When an item carrying such an “active” magnetic tag (not deactivated) passes through a magnetic field region (created by the external security system), the latter detects changes in the magnetic field caused by the response of the tag (of the soft magnetic strip) and generates an alarm signal. To deactivate the magnetic tag, it should be exposed to a D.C. or permanent magnetic field, which activates the hard magnetic strip (i.e., causes its magnetization), thereby preventing the detection of the soft magnetic strip response to the external AC magnetic field.
Hence, if the items are provided with security tags, the cashier removes the security tag from the purchased item or deactivates the tag remaining on the item, thereby preventing the tag from being detected by the magnetic security system mounted in an exit gate. Needless to say that this procedure is both time and manpower consuming, and is therefore inconvenient for both the customers and the store.
Techniques enabling customers to perform some of the above operations on their own have been developed, and disclosed, for example in U.S. Pat. Nos. 5,424,524 and 5,557,088. Generally, these techniques provide a customer with a self-scanning means that can be mounted on a shopping trolley, thereby enabling the customer to carry out the following: scan the bar code on a selected item, have its price displayed, scan his credit card identification code, add the displayed value to an existing list of purchased (scanned) items, and finalize the transaction.
According to the technique of U.S. Pat. No. 5,424,524, the customer is also provided with a magnetic security assembly of the kind capable of deactivating a magnetic security element attached to each item. To prevent unscrupulous shoppers from deactivating the security strips without actually scanning the barcode (to ensure payment for the item), a personal scanner device utilizes magnet coils, which create D.C. magnetic fields only when the barcode scanner is activated. In other words, the activation of the barcode scanner (by pushing the scan button) simultaneously causes the barcode scanning and routing of a direct current through the coils of electromagnets to create the required D.C. magnetic field to deactivate the magnetic tag. This, however, causes additional complicity for the customer, if he changes his mind about purchasing an item that has already been scanned.